Some vehicles are equipped with a “selectable transfer case,” which broadly includes any transfer case where the driver has the ability to select, choose and/or change its mode of operation. For example, in some vehicles the driver can choose between different lour-wheel modes' and ‘two-wheel modes’; this is particularly prevalent with trucks, sports utility vehicles (SUVs), cross-over vehicles, etc. A four-wheel mode, such as four-wheel hi (4H) or four-wheel low (4L), may be preferable if the vehicle is being driven on a gravel, wet, snowy, icy or uneven road surface or if it is hauling a heavy load. A two-wheel mode, like two-wheel hi (2H), is generally intended for dry pavement where the driver is more concerned with fuel economy. Depending on the particular vehicle, the driver may be able to select or change the transfer case mode by pushing a button or switch, engaging a lever or shifter, or by some other means.
Skilled artisans will appreciate that the different transfer case modes have both advantages and disadvantages. For instance, four-wheel modes typically get better traction than two-wheel modes, but they also usually suffer from lower fuel economy, and vice-versa. Drivers are sometimes known to inadvertently leave the transfer case in a non-optimal mode, such as when they leave the transfer case in a four-wheel mode even though the vehicle is currently being driven on flat, dry pavement where improved traction is no longer necessary. Thus, it may be desirable to notify or alert the driver as to when it is preferable to change transfer case modes.